Washington (CNN) - Sen. Tom Coburn, R-Oklahoma, who is a also a physician, told CNN he is convinced that Army Sgt. Bowe Bergdahl was drugged in the so-called "proof of life" video shown to senators during a closed briefing Wednesday.
When news broke of Bergdahl's release in exchange for five Guantanamo prisoners, administration officials cited Bergdahl's health as a driving factor in the decision to make the deal and get him home.
But in an exclusive interview with CNN, Coburn said he is convinced that Bergdahl "had been drugged" in the video, "either with an anti-psychotic or hypnotic drug," he said.
How could he tell?
"It's easy," Coburn replied, "His speech was slurred, he was having trouble reading, and he had what's called 'nystagmus.' I mean, he'd been obviously drugged. "
Coburn went on to emphasize that he was making that observation as a physician
"I'm speaking as a doctor, yeah," said Coburn.
Coburn is an obstetrician gynecologist.
The public has not seen this proof of life video, which is still classified.
When asked if it was possible that Bergdahl could have been beaten up, or sick – and not drugged, Coburn said: "Not at all. Not at all. That's a total response to medication."
He went on further to describe the way Bergdahl appeared on the video.
"First of all, very sleepy. Having trouble focusing, concentrating. Was staring at a card they were making him read. You couldn't see the card but you could see what he was doing. You could see his eyes, with what's caused 'nystagmus,' moving back and forth. You know, he was obviously drugged," said Coburn.
Coburn, a member of the Senate Intelligence Committee, also told CNN that Bergdahl "cleared a health check as he came into Germany."
"Now, his mental health is probably not, and his psychological health, but his physical health is fine," said Coburn,
The morning after Bergdahl's release, National Security Adviser Susan Rice told CNN's Candy Crowley they "had indications that indeed his health was growing more fragile. He had lost a good bit of weight, and we were very concerned that time was not something we could play with, that we
needed to act when we had the opportunity. And that's what we did."
Coburn, trying to be careful not to disclose classified information, told CNN Bergdahl's health was not the determining factor.
"That wasn't the basis– I can't comment any more outside– because most of it is classified, but I would say that's not the basis under which they made the decision," he said.